As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: SMOKE LAVATORY SMOKE POSTED INFLIGHT. THE FLIGHT CREW REPORTED THE DETECTION WAS 3L DOOR BUT COULD NOT CONFIRM THE SOURCE SINCE IT ONLY POSTED 4-5 SECONDS THEN EXTINGUISHED. MAINTENANCE PERFORMED OPERATIONAL CHECK OF LAVATORY L SMOKE DETECTION SYSTEM PER AMM 26-17-00 WITH NO ISSUES OR FAULTS NOTED.